The present invention relates to an apparatus for inflating an inflatable vehicle occupant protection device and, more particularly, to an autoignition material for a vehicle occupant protection apparatus.
An inflatable vehicle occupant protection device, such as an air bag, is deployed upon the occurrence of a vehicle crash. The air bag is part of a vehicle occupant protection apparatus, which further includes a crash sensor and an inflator. The inflator includes a housing, a gas generating material in the housing, and an igniter. The igniter is actuated so as to ignite the gas generating material when the vehicle experiences a collision for which inflation of the air bag is desired to protect the vehicle occupant. As the body of gas generating material burns, it generates a volume of inflation gas. The inflation gas is directed into the air bag to inflate the air bag. When the air bag is inflated, it expands into the vehicle occupant compartment and helps to protect the vehicle occupant.
Inflator housings may be formed from lightweight materials, such as aluminum. These lightweight materials can lose strength at abnormally high temperatures, such as those reached in a vehicle fire. At temperatures experienced in a vehicle fire, the gas generating material may autoignite and produce an inflation gas. The pressure of the inflation gas can cause the inflator housing to lose its structural integrity due to the reduced strength of the inflator housing material. To prevent such loss of structural integrity, inflators typically include an autoignition material that will autoignite and initiate combustion of the gas generating material at a temperature below that at which the material of the housing begins to lose a significant percentage of its strength.
U.S. Pat. No. 5,959,242 discloses an autoignition composition for safely initiating combustion of a main pyrotechnic charge in a gas generator or pyrotechnic device exposed to flame or a high temperature environment. The autoignition composition includes an oxidizer composition and metal powder.
The present invention is an autoignition material of a plurality of agglomerates. Each agglomerate comprises an oxidizer material particle. A plurality of metal fuel particles are disposed on the oxidizer material particle. The metal fuel particles are present in a weight ratio effective to substantially stoichiometrically balance the oxidizer material particle. The metal fuel particles exothermically react with the oxidizer material particle when the autoignition material is exposed to a temperature of about 80xc2x0 C. to about 250xc2x0 C. A thin binder film adheres the metal fuel particles to the oxidizer material particle and maintains the metal fuel particles in intimate contact with the oxidizer particle.